Method, apparatus and recording medium for recording time information for digital data streams

ABSTRACT

A method and apparatus for recording time information for received digital data streams are provided. The method includes recording first time information and second time information on a recording medium. The first time information is part of management data for managing presentation data and the second time information is time information of the presentation data. The format of the first time information coincides with the format of the second time information.

CROSS-REFERENCE

The present application is a continuation of U.S. patent applicationSer. No. 09/500,488 filed on Feb. 9, 2000 (now U.S. Pat. No. 6,789.072B1, issued Sep. 7, 2004) for which priority is claimed under 35 U.S.C.§120; and the present application claims priority of Patent ApplicationNo. 1999-04467 filed in Republic of Korea on Feb. 9, 1999 and PatentApplication No. 2000-00715 filed in Republic of Korea on Jan. 7, 2000,under 35 U.S.C. §119. The entire contents of each of these applicationsare herein fully incorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method and apparatus for creating andrecording time information for searching digital data streams to berecorded on a recording medium and a method and apparatus for searchingfor requested data using the created time information.

2. Description of the Related Art

In the conventional analog television broadcast, video signals aretransmitted over the air or through cables after being AM or FMmodulated. With the recent advance of digital technologies such asdigital image compression or digital modulation/demodulation,standardization for digital television broadcast is in rapid progress.Based upon the Moving Picture Experts Group (MPEG) format, satellite andcable broadcast industry also moves towards the digital broadcast.

The digital broadcast offers several advantages that its analogcounterpart cannot provide. For example, the digital broadcast iscapable of providing services with far more improved video/audioquality, transmitting several different programs within a fixedbandwidth, and offering enhanced compatibility with digitalcommunication media or digital storage media.

In the digital broadcast, a plurality of programs encoded based upon theMPEG format are multiplexed into a single transport stream beforetransmitted. The transmitted transport stream is received by a set topbox at the receiver and demultiplexed into original programs. If aprogram is chosen from among the demultiplexed programs, the chosenprogram is decoded by a decoder in the set top box and original audioand video signals are retrieved. The retrieved audio and video signalscan be presented by an A/V output apparatus such as a TV.

It is also possible to record the received digital broadcast signals ona storage medium instead of directly outputting the received broadcastsignals to A/V output devices. The stored digital broadcast signals canbe edited and retrieved afterwards. For example, a digital data streamreceived by the set top box can be transmitted to a streamer such as adigital video disk (DVD) recording apparatus through communicationinterfaces like an IEEE-1394 serial bus and stored on a recording mediumby the streamer. The recorded digital data stream can be edited andtransmitted back to the set top box so that the digital audio and videodata can be presented.

When recording the digital data stream of a single program on arecording medium in a streamer, the basic recording unit is a streamobject (SOB) comprising a series of stream object units (SOBUs). Torecord received digital data streams on a recording medium and toreproduce the recorded data afterwards, it is necessary to explore howto group and record stream objects (SOBs) and stream object units(SOBUs) and how to create search information for managing and searchingfor the recorded stream objects (SOBS) and stream object units (SOBUs).Also, it is required to investigate how to search a specific data streamcorresponding to a search time requested by a user.

A conventional method for recording digital data streams and creatingand recording navigation information will now be explained withreference to the accompanying drawings.

FIG. 1 depicts a block diagram of an apparatus in which the conventionalmethod for creating and recording the navigation information forrecorded digital data streams can be employed. FIG. 2 depicts theprocess of recording digital data streams and creating the navigationinformation in the system shown in FIG. 1. The system comprises a settop box 100, a communication interface (IEEE-1394), and a streamer 200.The set top box 100 receives transport streams encoded by systemencoders and broadcast by a plurality of broadcast stations anddemultiplexes the received transport streams. After a decoder 120decodes the transport stream of a program tuned by a tuning unit 110, acontrol unit 140 outputs the decoded transport stream to an A/V outputapparatus or to the streamer 200 through the IEEE-1394 communicationinterface 130 and 210 so that the transmitted program can be recorded ona recording medium 230 by the streamer 200, depending upon a user'schoice. When requested by a user, the streamer 200 retrieves therecorded program and transmits the retrieved program through theIEEE-1394 communication interface back to the set top box 100. In theset top box 100, the received program is decoded by the decoder 120 andthen outputted to an A/V output apparatus so that the recorded programcan be presented.

A control unit 250 of the streamer 200 controls a stream recording unit220 to record the data stream transmitted from the set top box 100 onthe recording medium 230, as shown in FIG. 2. The received data streamcomposed of transport stream packets is recorded on the recording mediumalong with the packet arrival time (PAT) of each transport streampacket. The transport stream packets with packet arrival times areorganized in sectors on the recording medium, with each sector having apredetermined size. A predetermined number of sectors, for example 32sectors, are grouped into a stream object unit (SOBU). If the recordingprocess is stopped or suspended by a user, the recorded stream objectunits (SOBUs) are grouped into a stream object (SOB). Additionally,navigation data such as the stream start application packet arrival time(S_S_APAT) and incremental application packet arrival time (IAPAT) formanaging and searching for the stream object (SOB) and stream objectunits (SOBUs) is recorded together with the transport stream packets onthe recording medium.

FIG. 3 shows the way the received digital data stream is recorded on therecording medium 230. An application packet and its packet arrival time(PAT or time stamp) constitute a transport stream packet (TSP). Aplurality of transport stream packets (TSPs) and header information areorganized into a sector and a predetermined number of sectors, forexample 32 sectors, constitute a stream object unit (SOBU). A series ofstream object units (SOBUs) constitutes a stream object (SOB).Meanwhile, the stream object information (SOBI), which is the navigationdata for managing and searching the recorded stream object (SOB),comprises stream object general information (SOB_GI) and a mapping list(MAPL) for managing stream object units (SOBUs) contained in the streamobject (SOB), as shown in FIGS. 4 and 5. The stream object generalinformation (SOB_GI) includes the stream start application packetarrival time (S_S_APAT) indicative of the start time of the associatedstream object (SOB). As shown in FIG. 2, the incremental applicationpacket arrival time (IAPAT), which is a count value counted at constanttime intervals (x) between two consecutive stream object units (SOBUs),is included in the mapping list (MAPL) and used as information forsearching for the associated stream object units (SOBUs).

The stream start application packet arrival time (S_S_APAT) contained inthe stream object general information (SOB_GI) is recorded as a 6-bytepacket arrival time (PAT) comprising a 9-bit packet arrival timeextension (PAT_ext) and a 39-bit packet arrival time base (PAT_base), asshown in FIG. 6( a). The packet arrival time extension (PAT_ext) is amodulo-300 counter that is incremented at a rate of 27 MHz, whereas thepacket arrival time base (PAT_base) is incremented at a rate of 90 kHz.Unlike the stream start application packet arrival time (S_S_APAT), thetime stamp recorded along with the application packet shown in FIG. 3 isrecorded as a 4-byte packet arrival time (PAT) as shown in FIG. 6( b)that is incremented at a rate of 27 MHz and thus can represent from 0 sup to 159 s (=232/27 MHz). As discussed above, the PAT of the transportstream packet as shown in FIG. 6( b) is a time stamp recorded along withan application packet, and is part of a SOB as shown in FIG. 3 where theSOB is part of user data (actual presentation data) recorded on therecording medium 230.

The method for searching for a transport stream packet corresponding torequested search time using the navigation and time informationregarding the stream object (SOB), stream object units (SOBUs) will beexplained in detail with reference to an example.

Suppose that the position (s) of a transport stream packet correspondingto the search time (ST) requested by a user is to be searched for, asshown in FIG. 2. First, the stream start application packet arrival time(S_S_APAT) contained in the stream object general information (SOB_GI)of each stream object (SOB) is compared with the requested search time(ST) and a stream start application packet arrival time (S_S_APAT) thatis closest to but does not exceed the request search time (ST) isdetected. Referring to the mapping list (MAPL) of the stream object SOB#1 containing the detected stream start application packet arrival time(S_S_APAT), the incremental application packet arrival time (IAPAT 1˜4)contained in the mapping list (MAPL) are summed up. The sum value ismultiplied by the unit time (x) and added to the detected stream startapplication packet arrival time (S₁₃ S_APAT). The procedure is repeateduntil the calculated value (S_S_APAT+x×ΣIAPAT) approaches the requestedsearch time (ST) without exceeding it. In FIG. 2, the summation andmultiplication is repeated to include IAPAT 4 because the calculatedvalue exceeds the search time (ST) if the calculation continues toIAPAT5. Then, the entry in the mapping list (MAPL) corresponding to thecalculated time (S_S_APAT+x×ΣIAPAT) is located and the index of theentry is multiplied by the number of sectors constituting a streamobject unit (for example, 32 sectors) to locate the desired streamobject unit SOBU 5.

From the start position A′ of the searched stream object SOBU 5, the4-byte packet arrival time (PAT), which is the time stamp of thetransport stream packet, is detected. Recall that the stream startapplication packet arrival time (S_S_APAT) and the packet arrival time(PAT) of a transport stream packet have different formats and thereforethe two values cannot be directly compared. For this reason, thedifference between the detected packet arrival time (PAT) and the packetarrival time of the first transport stream packet of the stream objectunit SOBU 5 is compared with the difference between the requested searchtime (ST) and the calculated value (S_S_APAT+x×ΣIAPAT) for fine searchof the transport stream packet corresponding to the requested searchtime (ST).

The position A searched based upon the time information(S_S_APAT+x×ΣIAPAT) calculated using the incremental application packetarrival times (IAPATs), however, does not coincide with the actual startposition A′ of the stream object unit SOBU 5, as shown in FIG. 2.Therefore, the offset between the transport stream packet position Adetected by the fine search operation and the actual position A′ resultsin a delay in the search operation.

As a result, additional information indicative of the offset valuebetween A′ and A (Offset_SZ in FIG. 2) is necessary for preciselysearching for the position (s) of the transport stream packetcorresponding to the requested search time (ST). It is not desirable,however, to add the additional information to every stream object unit(SOBU), which dramatically lowers the recording efficiency of therecording medium.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a recording medium,a method and an apparatus for recording time information associated withdigital data streams, which overcome the limitations and disadvantagesof the related art.

It is another object of the present invention to provide a method andapparatus for creating search information for recorded digital datastreams and a method and apparatus for searching digital data streamsusing the search information.

According to an aspect of the present invention, the time informationfor management and search of recorded digital data streams has the sametime base as the time information used in navigation data for digitaldata streams and thus no information on the position offset is required.The overflow of the packet arrival time due to insufficient length ofthe packet arrival time data is detected and correction of time data isperformed to prevent search error resulting from the overflow.

According to an aspect of the present invention, there is provided amethod of recording time information associated with digital datastreams, the method comprising the steps of: (a) recording first timeinformation on a recording medium, the first time information being partof management data for managing presentation data; and (b) recordingsecond time information on the recording medium, the second timeinformation being time information of the presentation data, wherein aformat of the first time information coincides with a format of thesecond time information.

According to an aspect of the present invention, there is provided anapparatus for recording time information associated with digital datastreams, the apparatus comprising a recording unit for recording firsttime information and second time information on a recording medium, thefirst time information being part of management data for managingpresentation data, the second time information being time information ofthe presentation data, wherein a format of the first time informationcoincides with a format of the second time information.

According to an aspect of the present invention, there is provided arecording medium for recording time information associated with digitaldata streams, the recording medium comprising: a recording layer; firsttime information stored on the recording layer, the first timeinformation being part of management data for managing presentationdata; and second time information stored on the recording layer, thesecond time information being time information of the presentation data,wherein a format of the first time information coincides with a formatof the second time information.

These and other objects of the present application will become morereadily apparent from the detailed description given hereinafter.However, it should be understood that the detailed description andspecific examples, while indicating preferred embodiments of theinvention, are given by way of illustration only, since various changesand modification within the spirit and scope of the invention willbecome apparent to those skilled in the art from this detaileddescription.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention, illustrate the preferred embodiments ofthe invention, and together with the description, serve to explain theprinciples of the present invention.

In the drawings:

FIG. 1 is a block diagram of an apparatus in which a general method forcreating and recording the navigation information for digital datastreams and for searching recorded digital data streams using thenavigation information can be employed;

FIG. 2 is a pictorial representation of a general process for creatingand recording the navigation information;

FIG. 3 is a pictorial representation showing the general hierarchicalstructure of a recorded digital data stream;

FIG. 4 is a table showing the general navigation information for arecorded data stream;

FIG. 5 is a table detailing a part of the general navigation informationof a recorded data stream;

FIG. 6 is a table showing the general time information for a recordeddata stream, wherein FIG. 6( a) shows 6-byte stream start applicationpacket arrival time (S_S_APAT) contained in a stream object generalinformation (SOB_GI) and FIG. 6( b) shows 4-byte packet arrival time(PAT) which is time stamp recorded with an application packet;

FIG. 7 is a table showing the time information for a recorded datastream according to an embodiment of the present invention, wherein FIG.7( a) shows 6-byte stream start application packet arrival time(S_S_APAT) contained in a stream object general information (SOB_GI) andFIG. 7( b) shows 4-byte packet arrival time (PAT) which is time stamprecorded with an application packet;

FIG. 8 is a pictorial representation of the reset indication informationaccording to an embodiment of the present invention;

FIG. 9 is a pictorial representation of the relation between a streamobject unit and the time information according to an embodiment of thepresent invention;

FIG. 10 is a pictorial representation of the packet arrival time oftransport stream packets recorded as 4-byte data; and

FIG. 11 is a pictorial representation showing the case where the arrivaltime information obtained in FIG. 10 differs from the actual packetarrival time.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In order that the invention may be fully understood, preferredembodiments thereof will now be described with reference to theaccompanying drawings. It is understood that the methods of the presentinvention can be implemented in the apparatus of FIG. 1 or otherapparatuses or systems. For the sake of easy understanding, the presentinvention will be discussed referring to the elements of FIG. 1.

FIGS. 7 and 8 depict the data format of the stream start applicationpacket arrival time (S_S_APAT) and the packet arrival time (PAT) of atransport stream packet in accordance with an embodiment of theinvention. When the control unit 250 of the streamer 200 records thestream start application packet arrival time (S_S_APAT) contained in thestream object general information (SOB_GI) on the recording medium 230,the stream start application packet arrival time (S_S_APAT) is recordedas 6-byte data as shown in FIG. 7( a) comprising a 9-bit packet arrivaltime extension (PAT_ext) and a 39-bit packet arrival time base(PAT_base) in accordance with the MPEG format. The stream startapplication packet arrival time (S_S_APAT) is part ofnavigation/management data.

In the stream start application packet arrival time (S_S_APAT), thepacket arrival time extension (PAT_ext) is a modulo-300 counter that isincremented at a rate of 27 MHz, whereas the packet arrival time base(PAT_base) is incremented at a rate of 90 kHz. On the other hand, thepacket arrival time (PAT) of a transport stream packet received throughthe communication interface 210 is 4-byte data as shown in FIG. 7( b)comprising a 9-bit packet arrival time extension (PAT_ext) and 23-bitpacket arrival time base (PAT_base). Like the stream start applicationpacket arrival time (S_S_APAT) in FIG. 7( a), the packet arrival timeextension (PAT_ext) in FIG. 7( b) is a modulo-300 counter that isincremented at a rate of 27 MHz and the packet arrival time base(PAT_base) is incremented at a rate of 90 kHz. The PAT of the transportstream packet shown in FIG. 7( b) is a time stamp recorded along with anapplication packet, and is part of a SOB as shown in FIG. 3.

In consequence, as shown in FIGS. 7( a) and 7(b), the 4-byte packetarrival time (PAT) of the transport stream packet has the same format asthe lower 4 bytes of the 6-byte stream start application packet arrivaltime (S_S_APAT). Thus, according to the present invention, the lower4-byte data of a stream start application packet arrival time (S_S_APAT)always coincides with one of the recorded 4-byte packet arrival times(PATs). Also, there is certainly a packet arrival time (PAT) coincidingwith the lower 4-byte data of the search time (ST) requested by a user,the 6-byte search time (ST) comprising a packet arrival time base(PAT_base) and a packet arrival time extension (PAT_ext) specified bythe MPEG format.

The 4-byte packet arrival time (PAT) of a transport stream packet canrepresent up to 93.2 s (93.2=223/90 kHz) since its packet arrival timebase (PAT_base) is 23-bit data that is incremented at a rate of 90 kHz.The packet arrival time (PAT) is reset to zero whenever the valuereaches the limit. The control unit 250 keeps examining occurrence ofreset. If reset occurs, the control unit 250 controls the streamrecording unit 220 to record information indicative of the occurrence ofreset (PAT_carry) in the header information area pertaining to a sectorcomprising a plurality of transport stream packets (TSPs) and headerinformation, as explained before with reference to FIG. 3.

The reset indication information is used in the case of data search. Thereset indication information (PAT_carry) as shown in FIG. 8 may berecorded as 1-bit data in the application header extension area, one ofheader information contained in the associated sector.

FIG. 9 shows the way the packet arrival time (PAT) of each transportstream packet is created when a digital data stream received by the settop box 100 is recorded by the streamer 200. It is assumed that a streamobject unit (SOBU) is made up of 32 sectors with each sector having 2048bytes and the transfer rate of the data stream is not higher than 10kbps. Hence, the time needed to record a stream object unit (SOBU) is52.4 s (52.4=32 sectors×2048 byte/10 kbps) and the packet arrival time(PAT) is reset at 93.2 s intervals.

In other words, a stream object unit is created every 52.4 s (S1, S2, .. . ), and the packet arrival time (PAT) is reset every 93.2 s (R1, R2,. . . ) and so the reset indication information (PAT_carry) is alsocreated every 93.2 s (C1, C2, . . . ). As a result, the packet arrivaltimes (PATs) of all transport stream packets belonging to a streamobject unit (SOBU) have mutually exclusive values as long as thetransfer rate of the digital data stream exceeds 10 kbps.

The method for searching for the position (s) of a transport streampacket corresponding to the search time (ST) requested by a user fromthe data stream recorded as shown in FIG. 9 will be explained withreference to FIG. 2. First, the stream start application packet arrivaltime (S_S_APAT) contained in the stream object general information(SOB_GI) of each stream object (SOB) is compared with the requestedsearch time (ST) and a stream start application packet arrival time(S_S_APAT) that is closest to but does not exceed the request searchtime (ST) is detected. Referring to the mapping list (MAPL) of thestream object SOB #1 containing the detected stream start applicationpacket arrival time (S_S_APAT), the incremental application packetarrival time (IAPAT 1˜4) contained in the mapping list (MAPL) are summedup. The sum value is multiplied by the unit time (x) and added to thestream start application packet arrival time (S_S_APAT). The procedureis repeated until the calculated value (S_S_APAT+x(ΣIAPAT)) approachesthe requested search time (ST) without exceeding it. In FIG. 2, thesummation and multiplication is repeated to include IAPAT 4 because thecalculated value (S_S_APAT+x(ΣIAPAT)) exceeds the search time (ST) ifthe calculation continues to IAPAT 5. The stream object corresponding tothe calculated value is SOBU 5, which corresponds to the upper 2-bytedata of the search time (ST) requested by the user.

From the start position A′ of the searched stream object SOBU 5, the4-byte packet arrival time (PAT) of each transport stream packet isdetected. The detected packet arrival time (PAT) is compared with thelower 2-byte data of the search time (ST) requested by the user to findthe transport stream packet (TS) the packet arrival time (PAT) of whichcoincides with the lower 2-byte data of the search time (ST).

In summary, using the stream start application packet arrival time(S_S_APAT) and incremental application packet arrival time (IAPAT)contained in the mapping list, the stream object unit SOBU5corresponding to the upper-unit time data of the requested search time(ST) is detected and then a transport stream packet the packet arrivaltime of which coincides with the lower-unit time data of the search time(ST) is detected. As a result, the position of the detected transportstream packet coincides with the requested search time (ST).

In this case, however, if the 4-byte packet arrival time added to eachtransport stream packet overflows after the start of the associatedstream object unit (SOBU) and before certain unit time elapses, theactual packet arrival time may become different from the arrival time ofthe first transport stream packet calculated based on the incrementalapplication packet arrival time in the mapping list. This case will beexplained in detail with reference to FIG. 10.

FIG. 10 depicts an example where the packet arrival time of eachtransport stream packet being received is recorded as 4-byte data. Inthis case, it is assumed that the unit time of the incrementalapplication packet arrival time (IAPAT) corresponds to the bit3 of the4th byte of the packet arrival time (the bit shaded in FIG. 10).Therefore, whenever the unit time elapses, the bit3 of the 4th byte istoggled.

In FIG. 10, the packet arrival time reference information ((a) in FIG.10) of the first transport stream packet of the nth stream object unit(SOBU #n) is FFFEDEFB₍₁₆₎ and the packet arrival time referenceinformation ((b) in FIG. 10) of the third transport stream packet isFFFFFEFF₍₁₆₎. Because the unit time elapses after the third transportstream packet arrives, the lower 4 bytes of the 6 bytes indicative ofthe packet arrival time are reset after the third transport streampacket arrives and before the unit time elapses and a carry ispropagated to the upper 2 bytes. Accordingly, the fifth transport streampacket, for example, has the arrival time reference information of00007EEFh, which is less than the previous value.

The upper 2 bytes of the actual packet arrival time of the firsttransport stream packet are 6EBE₍₁₆₎ but the value is not recorded onthe recording medium. In the case of data search, therefore, the upper 2bytes are calculated based on the incremental application packet arrivaltime (IAPAT) information. However, because a carry already exists beforethe first time duration of the unit time of the incremental applicationpacket arrival time (IAPAT) elapses within the associated stream objectunit (SOBU), the value of the upper 2 bytes obtained based on theincremental application packet arrival time (IAPAT) information isgreater than that of the upper 2 bytes of the actual packet arrival timeby 1. For this reason, in the case of data search, the upper 2 bytescalculated base on the incremental application packet arrival time(IAPAT) information should be not regarded as the upper 2 bytes prefixedto the 4-byte arrival time reference information detected from thetransport stream packet.

FIG. 11 depicts the case where a carry is generated as explained before.It is shown that the actual packet arrival time ((d) in FIG. 11) differsfrom the 6-byte packet arrival time ((c) in FIG. 11) comprising theupper 2 bytes ((b) in FIG. 11) calculated based on the incrementalapplication packet arrival time (IAPAT) information and the 4 bytearrival time reference information ((a) in FIG. 11) detected from thefirst transport stream packet.

In FIG. 11, the time information corresponding to a stream object unit(SOBU) calculated based on the incremental application packet arrivaltime (IAPAT) information is expressed by the upper 3 bytes and upper 6bits of the forth byte. This is because the unit time of the incrementalapplication packet arrival time (IAPAT) does not have time resolutionlower than 218 bits.

In order to compensate for the error in the calculated packet arrivaltime, therefore, it is inevitable to check whether the 4-byte packetarrival time reference information generated a carry after the firstpacket of an arbitrary stream object unit (SOBU) arrives and before theunit time of the incremental application packet arrival time (IAPAT)elapses.

To this end, the control unit 250 compares the lower 14 bits of the30-bit time information calculated based on the incremental applicationpacket arrival time (IAPAT) information with the upper 14 bits of the4-byte arrival time reference information of the first transport streampacket of the current stream object unit (SOBU) and concludes that acarry is generated if the latter is greater than the former. If so, thecontrol unit 250 subtracts the least significant bit of the upper2-bytes from the 30 bits calculated based on the incremental applicationpacket arrival time (IAPAT) information, takes the 2-byte result as theupper 2 bytes of the packet arrival time of the first transport streampacket of the associated stream object unit, and compares the packetarrival time with the requested search time.

In the example shown in FIG. 11, the number 11011110111110₍₂₎ is greaterthan the number 00000000000000₍₂₎ and thus the upper 2 bytes of thearrival time of the first transport stream packet is obtained bysubtracting 000100000000₍₁₆₎ from 6EBFXXXXXXXX₍₁₆₎ and taking the upper2 bytes from the result. As a result, the time information comprisingthe 2-byte data and the 4-byte packet arrival time detected from thetransport stream packet is used in the case of data search.

The existence of carry may be checked in a different manner. Forexample, the control unit 250 retrieves all data of the sectorsconstituting the associated stream object unit and checks the resetindication information (PAT_carry) recorded in the header information ineach sector. If any of the reset indication information indicates carry,the packet arrival time can be corrected by the aforementioned method.Otherwise, the upper 2 bytes of the value calculated based on theincremental application packet arrival time information can be used asthe upper 2 bytes of the packet arrival time.

As one skilled in the art would readily recognize, the recording medium230 can be, e.g., a DVD.

The invention may be embodied in other specific forms without departingfrom the sprit or essential characteristics thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

1. A method of recording time information associated with digital data,the method comprising the steps of: (a) recording first time informationon a recording medium, the first time information being part ofmanagement data for managing presentation data; and (b) recording secondtime information on the recording medium, the second time informationbeing time information of the presentation data, wherein a format of thefirst time information coincides with a format of the second timeinformation, and the format of each time information includes a basepart and an extension part, the base part having a value created by asmaller time unit and extension part having a value created by a biggertime unit.
 2. The method according to claim 1, wherein the presentationdata include video data.
 3. The method according to claim 2, whereineach of the first and second time information is represented in theformat of the extension part of packet arrival time extension and thebase part of packet arrival time base.
 4. The method according to claim3, wherein the packet arrival time extension is incremented at a rate of27 MHz, and the packet arrival time base is incremented at a rate of 90kHz.
 5. The method according to claim 2, wherein in the step (b), thepresentation data are represented in data object units, and the secondtime information is time information for each of the data object units.6. The method according to claim 5, wherein the data object units aregrouped into data objects, and in the step (a), the first timeinformation is time information for each of the data objects.
 7. Themethod according to claim 1, wherein the step (a) includes generatingthe first time information to be recorded on the recording medium, andthe step (b) includes generating the second time information to berecorded on the recording medium.
 8. The method according to claim 1,wherein in the steps (a) and (b), the recording medium is a DVD.
 9. Anapparatus for recording time information associated with digital data,the apparatus comprising: a recording unit recording first timeinformation and second time information on a recording medium, the firsttime information being part of management data for managing presentationdata, the second time information being time information of thepresentation data, wherein a format of the first time informationcoincides with a format of the second time information, and the formatof each time information includes a base part and an extension part, thebase part having a value created by a smaller time unit and extensionpart having a value created by a bigger time unit.
 10. The apparatusaccording to claim 9, wherein the presentation data include video data.11. The apparatus according to claim 10, wherein each of the first andsecond time information is represented in the format of the extensionpart of packet arrival time extension and the base part of packetarrival time base.
 12. The apparatus according to claim 11, wherein thepacket arrival time extension is incremented at a rate of 27 MHz, andthe packet arrival time base is incremented at a rate of 90 kHz.
 13. Theapparatus according to claim 10, wherein the presentation data arerepresented in data object units, and the second time information istime information for each of the data object units.
 14. The apparatusaccording to claim 13, wherein the data object units are grouped intodata objects, and the first time information is time information foreach of the data objects.
 15. The apparatus according to claim 9,further comprising: a generating unit generating the first timeinformation to be recorded on the recording medium; and generating thesecond time information to be recorded on the recording medium.
 16. Theapparatus according to claim 9, wherein the recording medium is a DVD.17. A recording medium for recording time information associated withdigital data, the recording medium comprising: a recording layer; firsttime information stored on the recording layer, the first timeinformation being part of management data for managing presentationdata; and second time information stored on the recording layer, thesecond time information being time information of the presentation data,wherein a format of the first time information coincides with a formatof the second time information, and the format of each time informationincludes a base part and an extension part, the base part having a valuecreated by a smaller time unit and extension part having a value createdby a bigger time unit.
 18. The recording medium according to claim 17,wherein the presentation data include video data.
 19. The recordingmedium according to claim 18, wherein each of the first and second timeinformation is represented in the format of the extension part of packetarrival time extension and the base part of packet arrival time base.20. The recording medium according to claim 19, wherein the packetarrival time extension is incremented at a rate of 27 MHz, and thepacket arrival time base is incremented at a rate of 90 kHz.
 21. Therecording medium according to claim 18, wherein the presentation dataare represented in data object units, and the second time information istime information for each of the data object units.
 22. The recordingmedium according to claim 21, wherein the data object units are groupedinto data objects, and the first time information is time informationfor each of the data objects.
 23. The recording medium according toclaim 17, wherein the recording medium is a DVD.
 24. The recordingmedium according to claim 22, wherein the first time informationindicates a presentation start time of each data object.
 25. Therecording medium according to claim 17, wherein the base part has a 90kHz unit value and the extension part has a 27 MHz unit value.
 26. Themethod according to claim 6, wherein the first time informationindicates a presentation start time of each data object.
 27. The methodaccording to claim 1, wherein the base part has a 90 kHz unit value andthe extension part has a 27 MHz unit value.
 28. The apparatus accordingto claim 14, wherein the first time information indicates a presentationstart time of each data object.
 29. The apparatus according to claim 9,wherein the base part has a 90 kHz unit value and the extension part hasa 27 MHz unit value.